WireGaugeCalc Free calculator · NEC cited · works offline
Dc Circuit Breaker Size For 4 Wire Gauge
Dc circuit breaker size for 4 wire gauge is simple with WireGaugeCalc, since you enter the conductor material and termination temperature and it returns the matching ampacity.
The tool reads the 4 AWG row of NEC 310.16, so you see the ampere value the breaker must protect.
You get a conductor and breaker pairing that holds up on inspection.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Matching 4 AWG Ampacity To A Breaker
Copper 4 AWG carries 70 amps at the 60 degree C column and 85 amps at 75 degrees C, so the termination temperature drives the rating.
Aluminum 4 AWG carries less, which changes the breaker you can use.
The calculator picks the column that matches your terminals so the breaker does not exceed conductor ampacity.
Why Conductor Material And Termination Temp Decide The Size
The tool ties the breaker to the real conductor rating:
- Choose copper or aluminum for the 4 AWG run.
- Set the termination temperature to 60 or 75 degrees C.
- Read the ampacity from NEC 310.16.
- See the standard breaker size at or below that value.
- Confirm both ends of the circuit use the same terminal rating.
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
What breaker size works with 4 AWG copper on DC?
Copper 4 AWG at the 75 degree C column is good for 85 amps, so an 80 amp breaker is a common match. DC sizing can carry added factors for solar and battery circuits, so verify against the current NEC and your local authority having jurisdiction.
Does DC change the conductor ampacity compared to AC?
The base conductor ampacity from NEC 310.16 is the same, but DC PV and battery circuits often add a 125 percent continuous current factor before sizing. Enter the corrected current so the breaker matches the conductor.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.